Like a floating exclamation point, a brushstroke on the breeze, a butterfly dances by us, eager to move onto the next bit of milkweed, or flowery front yard, or lush neighborhood. Stream Los Angeles ...

It's poetic, the notion that the flap of a butterfly's wing in Brazil can set off a cascade of atmospheric events that, weeks later, spurs the formation of a tornado in Texas. This so-called ...